Annular MTJ Electrode Structure to Reduce Barrier Shorts
Solution Overview
Problem
The challenges in manufacturing MRAM devices include tunnel barrier shorts due to metal re-sputtering during patterning of MTJ stacks and circular edge roughness (CER) resulting from grain boundaries in traditional hardmask materials, which affect the performance and reliability of MRAM devices.
Innovation Solution
The use of annular shaped electrodes with a dielectric underlayer and an amorphous dielectric hard mask for patterning the MTJ stack, preventing metal re-sputtering and reducing CER by ensuring well-defined interfaces and smooth surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional patterning methods are used, then manufacturing process is simple, but metal re-sputtering causes tunnel barrier shorts and circular edge roughness
Solution Approach 1:
A dielectric underlayer is introduced as an intermediary between the bottom electrode and the tunnel barrier. This dielectric layer acts as a protective mediator that prevents metal re-sputtering from reaching and shorting the tunnel barrier during the patterning process, thereby resolving the contradiction between maintaining simple patterning and preventing tunnel barrier shorts.
Solution Approach 2:
The dielectric underlayer is formed in advance before the metal layers are deposited and patterned. This preliminary action of creating the protective dielectric barrier beforehand prevents metal re-sputtering issues during subsequent patterning steps, eliminating tunnel barrier shorts without complicating the overall manufacturing process.
2Manufacturing precision
If traditional patterning methods are used, then manufacturing process is straightforward, but grain boundary defects cause circular edge roughness
Solution Approach 1:
The dielectric underlayer serves as an intermediary that eliminates grain boundary defects from the metal structure. By placing this dielectric barrier between the bottom electrode and the tunnel barrier, the harmful grain boundaries are prevented from causing circular edge roughness, thereby improving manufacturing precision without significantly complicating the patterning process.
3Reliability
If annular electrodes with dielectric underlayer are used, then metal re-sputtering is prevented, but device structure becomes more complex
Solution Approach 1:
The electrode structure is segmented by introducing a dielectric underlayer that divides the interface region. This segmentation creates distinct functional zones: the bottom electrode, the protective dielectric underlayer, and the tunnel barrier. This segmentation prevents metal re-sputtering while maintaining a manageable device structure through clear functional separation.
Solution Approach 2:
The dielectric underlayer acts as a disposable protective layer that is intentionally placed and later removed or integrated into the final structure. This temporary protective element prevents metal re-sputtering during manufacturing and can be eliminated in subsequent processing steps, reducing overall device complexity while maintaining reliability during critical manufacturing phases.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces the risk of tunnel barrier shorts and improves the performance of MRAM devices by minimizing metal re-sputtering and circular edge roughness, leading to enhanced electrical and magnetic properties with reduced variability.
Implementation Method 1
metal re-sputtering
Implementation Method 2
amorphous dielectric hard mask
Data Source
AI summary
A semiconductor device including a magnetic tunnel junction (MTJ) stack vertically aligned between an annular shaped bottom electrode and an annular shaped top electrode. A semiconductor device including a MTJ stack, vertically aligned between an annular shaped bottom electrode and an annular shaped top electrode, and an encapsulation layer surrounding vertical side surfaces of the MTJ stack, wherein the encapsulation layer does not surround the top electrode nor the bottom electrode. Forming a bottom electrode in a first inter-layer dielectric, forming a reference layer on the first inter-layer dielectric and on the bottom electrode, forming a tunnel barrier layer on the reference layer, forming a free layer on the tunnel barrier layer and patterning the reference layer, the tunnel barrier layer and the free layer into a magnetic tunnel function (MTJ) stack vertically aligned over the bottom electrode, while not patterning the bottom electrode nor the first inter-layer dielectric.